In processing a semiconductor substrate, the presence of contaminants on the substrate or a layer applied to a substrate can adversely affect subsequent processes or the performance of the finished semiconductor device. Contaminants can include undesirable oxides of metals applied to the substrate or residue from processes, such as mask residue from etching processes.
To remove the contaminants, substrate processing can include a non-selective etch process, for example, an etch using an ionized form of an inert gas such as argon. The etching process may take place in a chamber in which a plasma of an inert gas is formed above a substrate supported on a substrate support. In some cases the substrate support is coupled to a biasing radio frequency (RF) source to attract the argon molecules toward the substrate.
The inventors have observed that in etching procedures, non-uniformities in etch rate occur at the edge of the substrate. Under some processing conditions, the observed non-uniformities are significant and can adversely affect the substrate being processed.
Accordingly, the inventors have devised embodiments of substrate supports that may facilitate improved etch rate uniformity during plasma etching processes.